Webster's New World Medical Dictionary

prognosis
The forecast of the probable outcome
or course of a disease; the patient’s chance of
recovery.
prognostic
Pertaining to the prognosis, the out-
look for the patient.
progressive
Increasing in scope or severity,
advancing, or going forward. For example, a disease
that is progressive is worsening.
prokaryote
An organism whose cells lack a dis-
crete nucleus and other special subcellular com-
partments. Bacteria and viruses are prokaryotes.
Humans are not prokaryotes, but rather eukaryotes.
prolactin
A hormone secreted by the pituitary
gland that stimulates lactation (milk production). It
also has many other functions, including essential
roles in the maintenance of the immune system.
Abnormally high prolactin can delay puberty, inter-
fere with ovulation in women, decrease libido in
men, and decrease fertility. Elevated prolactin
(hyperprolactinemia) may be due to a benign
tumor in the pituitary gland called a prolactinoma.
prolactinoma
A benign tumor (called an ade-
noma) of the pituitary gland. Prolactinomas pro-
duce an excessive amount of the hormone
prolactin. Prolactinomas are the most common type
of pituitary tumor. Symptoms of prolactinoma are
caused by pressure of the tumor on surrounding tis-
sues or by excessive prolactin in the blood (hyper-
prolactinemia). Treatment may involve medications
and/or surgery. See also 
prolactin.
prolapsed uterus
See 
uterus, prolapsed.
prominent vertebra
The seventh cervical
(neck) vertebra, which has a long spinous process
that projects out from the back of its vertebral body.
promoter
In molecular biology, a site on DNA to
which the enzyme RNA polymerase can bind to ini-
tiate the transcription of DNA into RNA.